Helically wound cores are widely used for a variety of purposes. Cores can be intended for use by consumers and/or manufacturers. The products supported by the cores can include tape, yarn, paper, and other similar products. More specifically, such products supported by the cores can include sanitary tissues products, such as bath tissue and paper towels.
A helically wound core is formed by winding a material, such as paper stock, onto a cylindrical mandrel at a given wind angle, the material being wound such that each winding at least partially overlaps the previous winding and is adhered to itself at the seam or overlap to create a cylindrical core. Such cores are commonly used for rolled products where the rolled products are wound about the cores. The cores can provide stability to the rolled products during winding, shipping, dispensing, and storage of the rolled products. Typical paper cores can be made from pulp fiber and/or recycled pulp fiber.
In many applications, certain strength properties of cores for rolled products are important, especially depending on the type of product to be wound about the cores. Sufficiently high side-to-side, or radial, strength, for example, is important to ensure the cores can resist collapse when under side-to-side pressure during handling and shipping. Collapsed or partially collapsed cores cause the core to be misshaped during use, which negatively impacts consumer dispensing from a roll holder. Likewise, sufficiently high axial strength is important to provide crush-resistance of rolled products stacked vertically during storage and shipping. The core provides structural support and stability allowing for rolled products to be stacked on shipping pallets, for example, without collapse or distortion of the rolled product.
For paper cores radial strength and/or axial strength can be impacted by dimensional variations, such as core diameter and core wall thickness, or by material selection and processing. In general, core strength can be increased by increasing wall thickness (i.e., by increasing the paper basis weight or by adding layers,) and/or employing stronger plies (i.e., increasing strength through adding more fibers) for the layer or layers of the wound core. In regard to the latter, paper or paperboard is available in a wide variety of grades. In general, paper or paperboard strength can be improved by mechanical refining of paper pulp or paperboard pulp. Thus, a well-beaten pulp generally produces a stronger grade of paper or paperboard compared to a lightly beaten pulp. In addition, paper or paperboard strength can be improved by compressing (i.e., densifying) the paper or paperboard during manufacturing. Further, paper or paperboard strength is influenced by fiber type and quality. Generally, stronger paper or paperboard sheets have a higher density than lower strength paper or paperboard sheets. Stated differently, the above treatments generally result in an increase in paper or paperboard density along with an increase in paper or paperboard strength. These higher density, higher strength paper or paperboards are also more costly because of the additional fiber or material costs or processing costs.
In general, a core for a rolled product should have certain minimum strength properties to be able to maintain integrity and dimensions during manufacture and use. At the same time, the core manufacturer desires to minimize the cost of producing the cores by using fewer fibers, less materials, and/or less fiber processing.
Furthermore, manufacturers desire that consumers of rolled sheet products be able to identify their brand or logo for better brand awareness. Better brand awareness can result in higher levels of re-purchase of product.
Accordingly, there is a continuing unmet need for cores for rolled products that have reduced cost while maintaining sufficient strength properties.
Additionally, there is a continuing unmet need for cores for rolled products that can be optimized for cost and strength while being manufactured on existing roll-forming equipment.
Further, there is an unmet need for low cost, relatively high strength cores which can deliver other manufacturing or consumer benefits.
Further still, there is a continuing unmet need to provide consumer awareness of product branding before and after use.
Still further, there is a continuing unmet need for cores for rolled products that can exhibit branding or other indicia helpful for consumer awareness of brand identification.